text: /*
  ** sprintf.c - Kernel.#sprintf
  **
  ** See Copyright Notice in mruby.h
  */
  
  #include "mruby.h"
  
  #include <limits.h>
  #include <stdio.h>
  #include <string.h>
  #include "mruby/string.h"
  #include "mruby/hash.h"
  #include "mruby/numeric.h"
  #include <math.h>
  #include <ctype.h>
  
  #define BIT_DIGITS(N)   (((N)*146)/485 + 1)  /* log2(10) =~ 146/485 */
  #define BITSPERDIG MRB_INT_BIT
  #define EXTENDSIGN(n, l) (((~0 << (n)) >> (((n)*(l)) % BITSPERDIG)) & ~(~0 << (n)))
  
  mrb_value mrb_str_format(mrb_state *, int, const mrb_value *, mrb_value);
  static void fmt_setup(char*,size_t,int,int,mrb_int,mrb_int);
  
  static char*
  remove_sign_bits(char *str, int base)
  {
    char *t;
  
    t = str;
    if (base == 16) {
      while (*t == 'f') {
        t++;
      }
    }
    else if (base == 8) {
      *t |= EXTENDSIGN(3, strlen(t));
      while (*t == '7') {
        t++;
      }
    }
    else if (base == 2) {
      while (*t == '1') {
        t++;
      }
    }
  
    return t;
  }
  
  static char
  sign_bits(int base, const char *p)
  {
    char c;
  
    switch (base) {
    case 16:
      if (*p == 'X') c = 'F';
      else c = 'f';
      break;
    case 8:
      c = '7'; break;
    case 2:
      c = '1'; break;
    default:
      c = '.'; break;
    }
    return c;
  }
  
  static mrb_value
  mrb_fix2binstr(mrb_state *mrb, mrb_value x, int base)
  {
    char buf[64], *b = buf + sizeof buf;
    mrb_int num = mrb_fixnum(x);
    unsigned long val = (unsigned long)num;
    char d;
  
    if (base != 2) {
      mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid radix %S", mrb_fixnum_value(base));
    }
  
    if (val >= (1 << 10))
      val &= 0x3ff;
  
    if (val == 0) {
      return mrb_str_new_lit(mrb, "0");
    }
    *--b = '\0';
    do {
      *--b = mrb_digitmap[(int)(val % base)];
    } while (val /= base);
  
    if (num < 0) {
      b = remove_sign_bits(b, base);
      switch (base) {
      case 16: d = 'f'; break;
      case 8:  d = '7'; break;
      case 2:  d = '1'; break;
      default: d = 0;   break;
      }
  
      if (d && *b != d) {
        *--b = d;
      }
    }
  
    return mrb_str_new_cstr(mrb, b);
  }
  
  #define FNONE  0
  #define FSHARP 1
  #define FMINUS 2
  #define FPLUS  4
  #define FZERO  8
  #define FSPACE 16
  #define FWIDTH 32
  #define FPREC  64
  #define FPREC0 128
  
  #define CHECK(l) do {\
  /*  int cr = ENC_CODERANGE(result);*/\
    while (blen + (l) >= bsiz) {\
      bsiz*=2;\
    }\
    mrb_str_resize(mrb, result, bsiz);\
  /*  ENC_CODERANGE_SET(result, cr);*/\
    buf = RSTRING_PTR(result);\
  } while (0)
  
  #define PUSH(s, l) do { \
    CHECK(l);\
    memcpy(&buf[blen], s, l);\
    blen += (l);\
  } while (0)
  
  #define FILL(c, l) do { \
    CHECK(l);\
    memset(&buf[blen], c, l);\
    blen += (l);\
  } while (0)
  
  #define GETARG() (!mrb_undef_p(nextvalue) ? nextvalue : \
    posarg == -1 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "unnumbered(%S) mixed with numbered", mrb_fixnum_value(nextarg)), mrb_undef_value()) : \
    posarg == -2 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "unnumbered(%S) mixed with named", mrb_fixnum_value(nextarg)), mrb_undef_value()) : \
    (posarg = nextarg++, GETNTHARG(posarg)))
  
  #define GETPOSARG(n) (posarg > 0 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%S) after unnumbered(%S)", mrb_fixnum_value(n), mrb_fixnum_value(posarg)), mrb_undef_value()) : \
    posarg == -2 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "numbered(%S) after named", mrb_fixnum_value(n)), mrb_undef_value()) : \
    ((n < 1) ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid index - %S$", mrb_fixnum_value(n)), mrb_undef_value()) : \
    (posarg = -1, GETNTHARG(n))))
  
  #define GETNTHARG(nth) \
    ((nth >= argc) ? (mrb_raise(mrb, E_ARGUMENT_ERROR, "too few arguments"), mrb_undef_value()) : argv[nth])
  
  #define GETNAMEARG(id, name, len) ( \
    posarg > 0 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "named%S after unnumbered(%S)", mrb_str_new(mrb, (name), (len)), mrb_fixnum_value(posarg)), mrb_undef_value()) : \
    posarg == -1 ? \
    (mrb_raisef(mrb, E_ARGUMENT_ERROR, "named%S after numbered", mrb_str_new(mrb, (name), (len))), mrb_undef_value()) :    \
    (posarg = -2, mrb_hash_fetch(mrb, get_hash(mrb, &hash, argc, argv), id, mrb_undef_value())))
  
  #define GETNUM(n, val) \
    for (; p < end && ISDIGIT(*p); p++) {\
      int next_n = 10 * n + (*p - '0'); \
      if (next_n / 10 != n) {\
        mrb_raise(mrb, E_ARGUMENT_ERROR, #val " too big"); \
      } \
      n = next_n; \
    } \
    if (p >= end) { \
      mrb_raise(mrb, E_ARGUMENT_ERROR, "malformed format string - %*[0-9]"); \
    }
  
  #define GETASTER(num) do { \
    t = p++; \
    n = 0; \
    GETNUM(n, val); \
    if (*p == '$') { \
      tmp = GETPOSARG(n); \
    } \
    else { \
      tmp = GETARG(); \
      p = t; \
    } \
    num = mrb_fixnum(tmp); \
  } while (0)
  
  static mrb_value
  get_hash(mrb_state *mrb, mrb_value *hash, int argc, const mrb_value *argv)
  {
    mrb_value tmp;
  
    if (!mrb_undef_p(*hash)) return *hash;
    if (argc != 2) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "one hash required");
    }
    tmp = mrb_check_convert_type(mrb, argv[1], MRB_TT_HASH, "Hash", "to_hash");
    if (mrb_nil_p(tmp)) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "one hash required");
    }
    return (*hash = tmp);
  }
  
  /*
   *  call-seq:
   *     format(format_string [, arguments...] )   -> string
   *     sprintf(format_string [, arguments...] )  -> string
   *
   *  Returns the string resulting from applying <i>format_string</i> to
   *  any additional arguments.  Within the format string, any characters
   *  other than format sequences are copied to the result.
   *
   *  The syntax of a format sequence is follows.
   *
   *    %[flags][width][.precision]type
   *
   *  A format
   *  sequence consists of a percent sign, followed by optional flags,
   *  width, and precision indicators, then terminated with a field type
   *  character.  The field type controls how the corresponding
   *  <code>sprintf</code> argument is to be interpreted, while the flags
   *  modify that interpretation.
   *
   *  The field type characters are:
   *
   *      Field |  Integer Format
   *      ------+--------------------------------------------------------------
   *        b   | Convert argument as a binary number.
   *            | Negative numbers will be displayed as a two's complement
   *            | prefixed with `..1'.
   *        B   | Equivalent to `b', but uses an uppercase 0B for prefix
   *            | in the alternative format by #.
   *        d   | Convert argument as a decimal number.
   *        i   | Identical to `d'.
   *        o   | Convert argument as an octal number.
   *            | Negative numbers will be displayed as a two's complement
   *            | prefixed with `..7'.
   *        u   | Identical to `d'.
   *        x   | Convert argument as a hexadecimal number.
   *            | Negative numbers will be displayed as a two's complement
   *            | prefixed with `..f' (representing an infinite string of
   *            | leading 'ff's).
   *        X   | Equivalent to `x', but uses uppercase letters.
   *
   *      Field |  Float Format
   *      ------+--------------------------------------------------------------
   *        e   | Convert floating point argument into exponential notation
   *            | with one digit before the decimal point as [-]d.dddddde[+-]dd.
   *            | The precision specifies the number of digits after the decimal
   *            | point (defaulting to six).
   *        E   | Equivalent to `e', but uses an uppercase E to indicate
   *            | the exponent.
   *        f   | Convert floating point argument as [-]ddd.dddddd,
   *            | where the precision specifies the number of digits after
   *            | the decimal point.
   *        g   | Convert a floating point number using exponential form
   *            | if the exponent is less than -4 or greater than or
   *            | equal to the precision, or in dd.dddd form otherwise.
   *            | The precision specifies the number of significant digits.
   *        G   | Equivalent to `g', but use an uppercase `E' in exponent form.
   *        a   | Convert floating point argument as [-]0xh.hhhhp[+-]dd,
   *            | which is consisted from optional sign, "0x", fraction part
   *            | as hexadecimal, "p", and exponential part as decimal.
   *        A   | Equivalent to `a', but use uppercase `X' and `P'.
   *
   *      Field |  Other Format
   *      ------+--------------------------------------------------------------
   *        c   | Argument is the numeric code for a single character or
   *            | a single character string itself.
   *        p   | The valuing of argument.inspect.
   *        s   | Argument is a string to be substituted.  If the format
   *            | sequence contains a precision, at most that many characters
   *            | will be copied.
   *        %   | A percent sign itself will be displayed.  No argument taken.
   *
   *  The flags modifies the behavior of the formats.
   *  The flag characters are:
   *
   *    Flag     | Applies to    | Meaning
   *    ---------+---------------+-----------------------------------------
   *    space    | bBdiouxX      | Leave a space at the start of
   *             | aAeEfgG       | non-negative numbers.
   *             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
   *             |               | a minus sign with absolute value for
   *             |               | negative values.
   *    ---------+---------------+-----------------------------------------
   *    (digit)$ | all           | Specifies the absolute argument number
   *             |               | for this field.  Absolute and relative
   *             |               | argument numbers cannot be mixed in a
   *             |               | sprintf string.
   *    ---------+---------------+-----------------------------------------
   *     #       | bBoxX         | Use an alternative format.
   *             | aAeEfgG       | For the conversions `o', increase the precision
   *             |               | until the first digit will be `0' if
   *             |               | it is not formatted as complements.
   *             |               | For the conversions `x', `X', `b' and `B'
   *             |               | on non-zero, prefix the result with ``0x'',
   *             |               | ``0X'', ``0b'' and ``0B'', respectively.
   *             |               | For `a', `A', `e', `E', `f', `g', and 'G',
   *             |               | force a decimal point to be added,
   *             |               | even if no digits follow.
   *             |               | For `g' and 'G', do not remove trailing zeros.
   *    ---------+---------------+-----------------------------------------
   *    +        | bBdiouxX      | Add a leading plus sign to non-negative
   *             | aAeEfgG       | numbers.
   *             | (numeric fmt) | For `o', `x', `X', `b' and `B', use
   *             |               | a minus sign with absolute value for
   *             |               | negative values.
   *    ---------+---------------+-----------------------------------------
   *    -        | all           | Left-justify the result of this conversion.
   *    ---------+---------------+-----------------------------------------
   *    0 (zero) | bBdiouxX      | Pad with zeros, not spaces.
   *             | aAeEfgG       | For `o', `x', `X', `b' and `B', radix-1
   *             | (numeric fmt) | is used for negative numbers formatted as
   *             |               | complements.
   *    ---------+---------------+-----------------------------------------
   *    *        | all           | Use the next argument as the field width.
   *             |               | If negative, left-justify the result. If the
   *             |               | asterisk is followed by a number and a dollar
   *             |               | sign, use the indicated argument as the width.
   *
   *  Examples of flags:
   *
   *   # `+' and space flag specifies the sign of non-negative numbers.
   *   sprintf("%d", 123)  #=> "123"
   *   sprintf("%+d", 123) #=> "+123"
   *   sprintf("% d", 123) #=> " 123"
   *
   *   # `#' flag for `o' increases number of digits to show `0'.
   *   # `+' and space flag changes format of negative numbers.
   *   sprintf("%o", 123)   #=> "173"
   *   sprintf("%#o", 123)  #=> "0173"
   *   sprintf("%+o", -123) #=> "-173"
   *   sprintf("%o", -123)  #=> "..7605"
   *   sprintf("%#o", -123) #=> "..7605"
   *
   *   # `#' flag for `x' add a prefix `0x' for non-zero numbers.
   *   # `+' and space flag disables complements for negative numbers.
   *   sprintf("%x", 123)   #=> "7b"
   *   sprintf("%#x", 123)  #=> "0x7b"
   *   sprintf("%+x", -123) #=> "-7b"
   *   sprintf("%x", -123)  #=> "..f85"
   *   sprintf("%#x", -123) #=> "0x..f85"
   *   sprintf("%#x", 0)    #=> "0"
   *
   *   # `#' for `X' uses the prefix `0X'.
   *   sprintf("%X", 123)  #=> "7B"
   *   sprintf("%#X", 123) #=> "0X7B"
   *
   *   # `#' flag for `b' add a prefix `0b' for non-zero numbers.
   *   # `+' and space flag disables complements for negative numbers.
   *   sprintf("%b", 123)   #=> "1111011"
   *   sprintf("%#b", 123)  #=> "0b1111011"
   *   sprintf("%+b", -123) #=> "-1111011"
   *   sprintf("%b", -123)  #=> "..10000101"
   *   sprintf("%#b", -123) #=> "0b..10000101"
   *   sprintf("%#b", 0)    #=> "0"
   *
   *   # `#' for `B' uses the prefix `0B'.
   *   sprintf("%B", 123)  #=> "1111011"
   *   sprintf("%#B", 123) #=> "0B1111011"
   *
   *   # `#' for `e' forces to show the decimal point.
   *   sprintf("%.0e", 1)  #=> "1e+00"
   *   sprintf("%#.0e", 1) #=> "1.e+00"
   *
   *   # `#' for `f' forces to show the decimal point.
   *   sprintf("%.0f", 1234)  #=> "1234"
   *   sprintf("%#.0f", 1234) #=> "1234."
   *
   *   # `#' for `g' forces to show the decimal point.
   *   # It also disables stripping lowest zeros.
   *   sprintf("%g", 123.4)   #=> "123.4"
   *   sprintf("%#g", 123.4)  #=> "123.400"
   *   sprintf("%g", 123456)  #=> "123456"
   *   sprintf("%#g", 123456) #=> "123456."
   *
   *  The field width is an optional integer, followed optionally by a
   *  period and a precision.  The width specifies the minimum number of
   *  characters that will be written to the result for this field.
   *
   *  Examples of width:
   *
   *   # padding is done by spaces,       width=20
   *   # 0 or radix-1.             <------------------>
   *   sprintf("%20d", 123)   #=> "                 123"
   *   sprintf("%+20d", 123)  #=> "                +123"
   *   sprintf("%020d", 123)  #=> "00000000000000000123"
   *   sprintf("%+020d", 123) #=> "+0000000000000000123"
   *   sprintf("% 020d", 123) #=> " 0000000000000000123"
   *   sprintf("%-20d", 123)  #=> "123                 "
   *   sprintf("%-+20d", 123) #=> "+123                "
   *   sprintf("%- 20d", 123) #=> " 123                "
   *   sprintf("%020x", -123) #=> "..ffffffffffffffff85"
   *
   *  For
   *  numeric fields, the precision controls the number of decimal places
   *  displayed.  For string fields, the precision determines the maximum
   *  number of characters to be copied from the string.  (Thus, the format
   *  sequence <code>%10.10s</code> will always contribute exactly ten
   *  characters to the result.)
   *
   *  Examples of precisions:
   *
   *   # precision for `d', 'o', 'x' and 'b' is
   *   # minimum number of digits               <------>
   *   sprintf("%20.8d", 123)  #=> "            00000123"
   *   sprintf("%20.8o", 123)  #=> "            00000173"
   *   sprintf("%20.8x", 123)  #=> "            0000007b"
   *   sprintf("%20.8b", 123)  #=> "            01111011"
   *   sprintf("%20.8d", -123) #=> "           -00000123"
   *   sprintf("%20.8o", -123) #=> "            ..777605"
   *   sprintf("%20.8x", -123) #=> "            ..ffff85"
   *   sprintf("%20.8b", -11)  #=> "            ..110101"
   *
   *   # "0x" and "0b" for `#x' and `#b' is not counted for
   *   # precision but "0" for `#o' is counted.  <------>
   *   sprintf("%#20.8d", 123)  #=> "            00000123"
   *   sprintf("%#20.8o", 123)  #=> "            00000173"
   *   sprintf("%#20.8x", 123)  #=> "          0x0000007b"
   *   sprintf("%#20.8b", 123)  #=> "          0b01111011"
   *   sprintf("%#20.8d", -123) #=> "           -00000123"
   *   sprintf("%#20.8o", -123) #=> "            ..777605"
   *   sprintf("%#20.8x", -123) #=> "          0x..ffff85"
   *   sprintf("%#20.8b", -11)  #=> "          0b..110101"
   *
   *   # precision for `e' is number of
   *   # digits after the decimal point           <------>
   *   sprintf("%20.8e", 1234.56789) #=> "      1.23456789e+03"
   *
   *   # precision for `f' is number of
   *   # digits after the decimal point               <------>
   *   sprintf("%20.8f", 1234.56789) #=> "       1234.56789000"
   *
   *   # precision for `g' is number of
   *   # significant digits                          <------->
   *   sprintf("%20.8g", 1234.56789) #=> "           1234.5679"
   *
   *   #                                         <------->
   *   sprintf("%20.8g", 123456789)  #=> "       1.2345679e+08"
   *
   *   # precision for `s' is
   *   # maximum number of characters                    <------>
   *   sprintf("%20.8s", "string test") #=> "            string t"
   *
   *  Examples:
   *
   *     sprintf("%d %04x", 123, 123)               #=> "123 007b"
   *     sprintf("%08b '%4s'", 123, 123)            #=> "01111011 ' 123'"
   *     sprintf("%1$*2$s %2$d %1$s", "hello", 8)   #=> "   hello 8 hello"
   *     sprintf("%1$*2$s %2$d", "hello", -8)       #=> "hello    -8"
   *     sprintf("%+g:% g:%-g", 1.23, 1.23, 1.23)   #=> "+1.23: 1.23:1.23"
   *     sprintf("%u", -123)                        #=> "-123"
   *
   *  For more complex formatting, Ruby supports a reference by name.
   *  %<name>s style uses format style, but %{name} style doesn't.
   *
   *  Exapmles:
   *    sprintf("%<foo>d : %<bar>f", { :foo => 1, :bar => 2 })
   *      #=> 1 : 2.000000
   *    sprintf("%{foo}f", { :foo => 1 })
   *      # => "1f"
   */
  
  mrb_value
  mrb_f_sprintf(mrb_state *mrb, mrb_value obj)
  {
    mrb_int argc;
    mrb_value *argv;
  
    mrb_get_args(mrb, "*", &argv, &argc);
  
    if (argc <= 0) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "too few arguments");
      return mrb_nil_value();
    }
    else {
      return mrb_str_format(mrb, argc - 1, argv + 1, argv[0]);
    }
  }
  
  mrb_value
  mrb_str_format(mrb_state *mrb, int argc, const mrb_value *argv, mrb_value fmt)
  {
    const char *p, *end;
    char *buf;
    mrb_int blen;
    mrb_int bsiz;
    mrb_value result;
    mrb_int n;
    mrb_int width;
    mrb_int prec;
    int flags = FNONE;
    int nextarg = 1;
    int posarg = 0;
    mrb_value nextvalue;
    mrb_value tmp;
    mrb_value str;
    mrb_value hash = mrb_undef_value();
  
  #define CHECK_FOR_WIDTH(f)                                                  \
    if ((f) & FWIDTH) {                                                       \
      mrb_raise(mrb, E_ARGUMENT_ERROR, "width given twice");         \
    }                                                                         \
    if ((f) & FPREC0) {                                                       \
      mrb_raise(mrb, E_ARGUMENT_ERROR, "width after precision");     \
    }
  #define CHECK_FOR_FLAGS(f)                                                  \
    if ((f) & FWIDTH) {                                                       \
      mrb_raise(mrb, E_ARGUMENT_ERROR, "flag after width");          \
    }                                                                         \
    if ((f) & FPREC0) {                                                       \
      mrb_raise(mrb, E_ARGUMENT_ERROR, "flag after precision");      \
    }
  
    ++argc;
    --argv;
    fmt = mrb_str_to_str(mrb, fmt);
    p = RSTRING_PTR(fmt);
    end = p + RSTRING_LEN(fmt);
    blen = 0;
    bsiz = 120;
    result = mrb_str_buf_new(mrb, bsiz);
    buf = RSTRING_PTR(result);
    memset(buf, 0, bsiz);
  
    for (; p < end; p++) {
      const char *t;
      mrb_sym id = 0;
  
      for (t = p; t < end && *t != '%'; t++) ;
      PUSH(p, t - p);
      if (t >= end)
        goto sprint_exit; /* end of fmt string */
  
      p = t + 1;    /* skip `%' */
  
      width = prec = -1;
      nextvalue = mrb_undef_value();
  
  retry:
      switch (*p) {
        default:
          mrb_raisef(mrb, E_ARGUMENT_ERROR, "malformed format string - \\%%S", mrb_str_new(mrb, p, 1));
          break;
  
        case ' ':
          CHECK_FOR_FLAGS(flags);
          flags |= FSPACE;
          p++;
          goto retry;
  
        case '#':
          CHECK_FOR_FLAGS(flags);
          flags |= FSHARP;
          p++;
          goto retry;
  
        case '+':
          CHECK_FOR_FLAGS(flags);
          flags |= FPLUS;
          p++;
          goto retry;
  
        case '-':
          CHECK_FOR_FLAGS(flags);
          flags |= FMINUS;
          p++;
          goto retry;
  
        case '0':
          CHECK_FOR_FLAGS(flags);
          flags |= FZERO;
          p++;
          goto retry;
  
        case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9':
          n = 0;
          GETNUM(n, width);
          if (*p == '$') {
            if (!mrb_undef_p(nextvalue)) {
              mrb_raisef(mrb, E_ARGUMENT_ERROR, "value given twice - %S$", mrb_fixnum_value(n));
            }
            nextvalue = GETPOSARG(n);
            p++;
            goto retry;
          }
          CHECK_FOR_WIDTH(flags);
          width = n;
          flags |= FWIDTH;
          goto retry;
  
        case '<':
        case '{': {
          const char *start = p;
          char term = (*p == '<') ? '>' : '}';
          mrb_value symname;
  
          for (; p < end && *p != term; )
            p++;
          if (id) {
            mrb_raisef(mrb, E_ARGUMENT_ERROR, "name%S after <%S>",
                       mrb_str_new(mrb, start, p - start + 1), mrb_sym2str(mrb, id));
          }
          symname = mrb_str_new(mrb, start + 1, p - start - 1);
          id = mrb_intern_str(mrb, symname);
          nextvalue = GETNAMEARG(mrb_symbol_value(id), start, (int)(p - start + 1));
          if (mrb_undef_p(nextvalue)) {
            mrb_raisef(mrb, E_KEY_ERROR, "key%S not found", mrb_str_new(mrb, start, p - start + 1));
          }
          if (term == '}') goto format_s;
          p++;
          goto retry;
        }
  
        case '*':
          CHECK_FOR_WIDTH(flags);
          flags |= FWIDTH;
          GETASTER(width);
          if (width < 0) {
            flags |= FMINUS;
            width = -width;
          }
          p++;
          goto retry;
  
        case '.':
          if (flags & FPREC0) {
            mrb_raise(mrb, E_ARGUMENT_ERROR, "precision given twice");
          }
          flags |= FPREC|FPREC0;
  
          prec = 0;
          p++;
          if (*p == '*') {
            GETASTER(prec);
            if (prec < 0) {  /* ignore negative precision */
              flags &= ~FPREC;
            }
            p++;
            goto retry;
          }
  
          GETNUM(prec, precision);
          goto retry;
  
        case '\n':
        case '\0':
          p--;
          /* fallthrough */
        case '%':
          if (flags != FNONE) {
            mrb_raise(mrb, E_ARGUMENT_ERROR, "invalid format character - %");
          }
          PUSH("%", 1);
          break;
  
        case 'c': {
          mrb_value val = GETARG();
          mrb_value tmp;
          char *c;
  
          tmp = mrb_check_string_type(mrb, val);
          if (!mrb_nil_p(tmp)) {
            if (mrb_fixnum(mrb_funcall(mrb, tmp, "size", 0)) != 1 ) {
              mrb_raise(mrb, E_ARGUMENT_ERROR, "%c requires a character");
            }
          }
          else if (mrb_fixnum_p(val)) {
            tmp = mrb_funcall(mrb, val, "chr", 0);
          }
          else {
            mrb_raise(mrb, E_ARGUMENT_ERROR, "invalid character");
          }
          c = RSTRING_PTR(tmp);
          n = RSTRING_LEN(tmp);
          if (!(flags & FWIDTH)) {
            CHECK(n);
            memcpy(buf+blen, c, n);
            blen += n;
          }
          else if ((flags & FMINUS)) {
            CHECK(n);
            memcpy(buf+blen, c, n);
            blen += n;
            FILL(' ', width-1);
          }
          else {
            FILL(' ', width-1);
            CHECK(n);
            memcpy(buf+blen, c, n);
            blen += n;
          }
        }
        break;
  
        case 's':
        case 'p':
    format_s:
        {
          mrb_value arg = GETARG();
          mrb_int len;
          mrb_int slen;
  
          if (*p == 'p') arg = mrb_inspect(mrb, arg);
          str = mrb_obj_as_string(mrb, arg);
          len = RSTRING_LEN(str);
          if (RSTRING(result)->flags & MRB_STR_EMBED) {
            mrb_int tmp_n = len;
            RSTRING(result)->flags &= ~MRB_STR_EMBED_LEN_MASK;
            RSTRING(result)->flags |= tmp_n << MRB_STR_EMBED_LEN_SHIFT;
          } else {
            RSTRING(result)->as.heap.len = blen;
          }
          if (flags&(FPREC|FWIDTH)) {
            slen = RSTRING_LEN(str);
            if (slen < 0) {
              mrb_raise(mrb, E_ARGUMENT_ERROR, "invalid mbstring sequence");
            }
            if ((flags&FPREC) && (prec < slen)) {
              char *p = RSTRING_PTR(str) + prec;
              slen = prec;
              len = p - RSTRING_PTR(str);
            }
            /* need to adjust multi-byte string pos */
            if ((flags&FWIDTH) && (width > slen)) {
              width -= (int)slen;
              if (!(flags&FMINUS)) {
                CHECK(width);
                while (width--) {
                  buf[blen++] = ' ';
                }
              }
              CHECK(len);
              memcpy(&buf[blen], RSTRING_PTR(str), len);
              blen += len;
              if (flags&FMINUS) {
                CHECK(width);
                while (width--) {
                  buf[blen++] = ' ';
                }
              }
              break;
            }
          }
          PUSH(RSTRING_PTR(str), len);
        }
        break;
  
        case 'd':
        case 'i':
        case 'o':
        case 'x':
        case 'X':
        case 'b':
        case 'B':
        case 'u': {
          mrb_value val = GETARG();
          char fbuf[32], nbuf[64], *s;
          const char *prefix = NULL;
          int sign = 0, dots = 0;
          char sc = 0;
          mrb_int v = 0, org_v = 0;
          int base;
          mrb_int len;
  
          switch (*p) {
            case 'd':
            case 'i':
            case 'u':
              sign = 1; break;
            case 'o':
            case 'x':
            case 'X':
            case 'b':
            case 'B':
              if (flags&(FPLUS|FSPACE)) sign = 1;
              break;
            default:
              break;
          }
          if (flags & FSHARP) {
            switch (*p) {
              case 'o': prefix = "0"; break;
              case 'x': prefix = "0x"; break;
              case 'X': prefix = "0X"; break;
              case 'b': prefix = "0b"; break;
              case 'B': prefix = "0B"; break;
              default: break;
            }
          }
  
    bin_retry:
          switch (mrb_type(val)) {
            case MRB_TT_FLOAT:
              if (FIXABLE(mrb_float(val))) {
                val = mrb_fixnum_value((mrb_int)mrb_float(val));
                goto bin_retry;
              }
              val = mrb_flo_to_fixnum(mrb, val);
              if (mrb_fixnum_p(val)) goto bin_retry;
              break;
            case MRB_TT_STRING:
              val = mrb_str_to_inum(mrb, val, 0, TRUE);
              goto bin_retry;
            case MRB_TT_FIXNUM:
              v = mrb_fixnum(val);
              break;
            default:
              val = mrb_Integer(mrb, val);
              goto bin_retry;
          }
  
          switch (*p) {
            case 'o':
              base = 8; break;
            case 'x':
            case 'X':
              base = 16; break;
            case 'b':
            case 'B':
              base = 2; break;
            case 'u':
            case 'd':
            case 'i':
            default:
              base = 10; break;
          }
  
          if (base == 2) {
            org_v = v;
            if ( v < 0 && !sign ) {
              val = mrb_fix2binstr(mrb, mrb_fixnum_value(v), base);
              dots = 1;
            }
            else {
              val = mrb_fixnum_to_str(mrb, mrb_fixnum_value(v), base);
            }
            v = mrb_fixnum(mrb_str_to_inum(mrb, val, 10, FALSE));
          }
          if (sign) {
            char c = *p;
            if (c == 'i') c = 'd'; /* %d and %i are identical */
            if (base == 2) c = 'd';
            if (v < 0) {
              v = -v;
              sc = '-';
              width--;
            }
            else if (flags & FPLUS) {
              sc = '+';
              width--;
            }
            else if (flags & FSPACE) {
              sc = ' ';
              width--;
            }
            snprintf(fbuf, sizeof(fbuf), "%%l%c", c);
            snprintf(nbuf, sizeof(nbuf), fbuf, v);
            s = nbuf;
          }
          else {
            char c = *p;
            if (c == 'X') c = 'x';
            if (base == 2) c = 'd';
            s = nbuf;
            if (v < 0) {
              dots = 1;
            }
            snprintf(fbuf, sizeof(fbuf), "%%l%c", c);
            snprintf(++s, sizeof(nbuf) - 1, fbuf, v);
            if (v < 0) {
              char d;
  
              s = remove_sign_bits(s, base);
              switch (base) {
                case 16: d = 'f'; break;
                case 8:  d = '7'; break;
                case 2:  d = '1'; break;
                default: d = 0; break;
              }
  
              if (d && *s != d) {
                *--s = d;
              }
            }
          }
          {
            size_t size;
            size = strlen(s);
            /* PARANOID: assert(size <= MRB_INT_MAX) */
            len = (mrb_int)size;
          }
  
          if (dots) {
            prec -= 2;
            width -= 2;
          }
  
          if (*p == 'X') {
            char *pp = s;
            int c;
            while ((c = (int)(unsigned char)*pp) != 0) {
              *pp = toupper(c);
              pp++;
            }
          }
  
          if (prefix && !prefix[1]) { /* octal */
            if (dots) {
              prefix = NULL;
            }
            else if (len == 1 && *s == '0') {
              len = 0;
              if (flags & FPREC) prec--;
            }
            else if ((flags & FPREC) && (prec > len)) {
              prefix = NULL;
            }
          }
          else if (len == 1 && *s == '0') {
            prefix = NULL;
          }
  
          if (prefix) {
            size_t size;
            size = strlen(prefix);
            /* PARANOID: assert(size <= MRB_INT_MAX).
             *  this check is absolutely paranoid. */
            width -= (mrb_int)size;
          }
  
          if ((flags & (FZERO|FMINUS|FPREC)) == FZERO) {
            prec = width;
            width = 0;
          }
          else {
            if (prec < len) {
              if (!prefix && prec == 0 && len == 1 && *s == '0') len = 0;
              prec = len;
            }
            width -= prec;
          }
  
          if (!(flags&FMINUS)) {
            CHECK(width);
            while (width-- > 0) {
              buf[blen++] = ' ';
            }
          }
  
          if (sc) PUSH(&sc, 1);
  
          if (prefix) {
            int plen = (int)strlen(prefix);
            PUSH(prefix, plen);
          }
          CHECK(prec - len);
          if (dots) PUSH("..", 2);
  
          if (v < 0 || (base == 2 && org_v < 0)) {
            char c = sign_bits(base, p);
            while (len < prec--) {
              buf[blen++] = c;
            }
          }
          else if ((flags & (FMINUS|FPREC)) != FMINUS) {
            char c = '0';
            while (len < prec--) {
              buf[blen++] = c;
            }
          }
  
          PUSH(s, len);
          CHECK(width);
          while (width-- > 0) {
            buf[blen++] = ' ';
          }
        }
        break;
  
        case 'f':
        case 'g':
        case 'G':
        case 'e':
        case 'E':
        case 'a':
        case 'A': {
          mrb_value val = GETARG();
          double fval;
          int i, need = 6;
          char fbuf[32];
  
          fval = mrb_float(mrb_Float(mrb, val));
          if (isnan(fval) || isinf(fval)) {
            const char *expr;
            const int elen = 3;
  
            if (isnan(fval)) {
              expr = "NaN";
            }
            else {
              expr = "Inf";
            }
            need = elen;
            if ((!isnan(fval) && fval < 0.0) || (flags & FPLUS))
              need++;
            if ((flags & FWIDTH) && need < width)
              need = width;
  
            CHECK(need + 1);
            snprintf(&buf[blen], need + 1, "%*s", need, "");
            if (flags & FMINUS) {
              if (!isnan(fval) && fval < 0.0)
                buf[blen++] = '-';
              else if (flags & FPLUS)
                buf[blen++] = '+';
              else if (flags & FSPACE)
                blen++;
              memcpy(&buf[blen], expr, elen);
            }
            else {
              if (!isnan(fval) && fval < 0.0)
                buf[blen + need - elen - 1] = '-';
              else if (flags & FPLUS)
                buf[blen + need - elen - 1] = '+';
              else if ((flags & FSPACE) && need > width)
                blen++;
              memcpy(&buf[blen + need - elen], expr, elen);
            }
            blen += strlen(&buf[blen]);
            break;
          }
  
          fmt_setup(fbuf, sizeof(fbuf), *p, flags, width, prec);
          need = 0;
          if (*p != 'e' && *p != 'E') {
            i = INT_MIN;
            frexp(fval, &i);
            if (i > 0)
              need = BIT_DIGITS(i);
          }
          need += (flags&FPREC) ? prec : 6;
          if ((flags&FWIDTH) && need < width)
            need = width;
          need += 20;
  
          CHECK(need);
          n = snprintf(&buf[blen], need, fbuf, fval);
          blen += n;
        }
        break;
      }
      flags = FNONE;
    }
  
    sprint_exit:
  #if 0
    /* XXX - We cannot validate the number of arguments if (digit)$ style used.
     */
    if (posarg >= 0 && nextarg < argc) {
      const char *mesg = "too many arguments for format string";
      if (mrb_test(ruby_debug)) mrb_raise(mrb, E_ARGUMENT_ERROR, mesg);
      if (mrb_test(ruby_verbose)) mrb_warn(mrb, "%S", mrb_str_new_cstr(mrb, mesg));
    }
  #endif
    mrb_str_resize(mrb, result, blen);
  
    return result;
  }
  
  static void
  fmt_setup(char *buf, size_t size, int c, int flags, mrb_int width, mrb_int prec)
  {
    char *end = buf + size;
    int n;
  
    *buf++ = '%';
    if (flags & FSHARP) *buf++ = '#';
    if (flags & FPLUS)  *buf++ = '+';
    if (flags & FMINUS) *buf++ = '-';
    if (flags & FZERO)  *buf++ = '0';
    if (flags & FSPACE) *buf++ = ' ';
  
    if (flags & FWIDTH) {
      n = snprintf(buf, end - buf, "%d", (int)width);
      buf += n;
    }
  
    if (flags & FPREC) {
      n = snprintf(buf, end - buf, ".%d", (int)prec);
      buf += n;
    }
  
    *buf++ = c;
    *buf = '\0';
  }
  